trigger point injections for post-mastectomy pain syndrome

Conditions: Post-mastectomy Pain Syndrome; Myofascial Pain Syndrome; Trigger Point Pain, Myofascial; Breast Cancer

Summary: post-mastectomy pain syndrome (pmps) is a chronic pain that persists for more than three months after a surgical breast procedure. it has 11-70% incidence in patients that underwent a breast surgery. it consists of mixed pain, frequently associated with myofascial pain, an specific type of muscular pain. trigger point injections (tpi) are classically used for the treatment of myofascial pain in other painful conditions. however, there are no controlled trials assessing the efficacy of tpi in the treatment of pmps. the intervention objective is to assess the efficacy of tpi in patients with pmps, when associated with a comprehensive rehabilitation program and pain management.

introduction: post-mastectomy pain syndrome (pmps) is a chronic pain that persists for more than three months after a surgical breast procedure. it has 11-70% incidence in patients that underwent a breast surgery. it consists of mixed pain, frequently associated with myofascial pain. trigger point injections (tpi) are classically used for the treatment of myofascial pain in other etiologies. however, there are no controlled trials assessing the efficacy of tpi in the treatment of pmps objective: assess the efficacy of tpi in patients with pmps, when associated with a comprehensive rehabilitation program and pain management. methods: double-blind randomized controlled trial with intention-to-treat analysis. both groups will undergo standard of care delivered by physiatrist blinded to group allocation. active group will undergo tpi with 1% lidocaine in each identified trigger-point, weekly, for three consecutive weeks. control group will undergo subcutaneous saline injection superficial to the same trigger points, with the same frequency and number of sessions. primary outcome is the mean difference between groups for pain levels, as assessed by visual numeric scale (vns), from baseline to 3 months after the procedure. statistical analysis: difference between groups at baseline, one and three months after injection, using analysis of covariance (ancova) for the following outcomes: vns; presence of active trigger points, pressure pain threshold (ppt); short-form mcgill pain questionnaire (sf-mpq); neuropathic pain symptom inventory (npsi); disabilities of the arm, shoulder and hand questionnaire (dash); range of motion (rom) of affected shoulder, for abduction and external rotation; adverse events; use of pain medication. total sample size is 120. alpha=5%, power=80%.

Eligibility criteria:
inclusion criteria: * breast cancer patients. * pmps diagnosis, as per wisotzky et col. * pain \> 3 months over breast, chest wall or shoulder ipsilateral to surgery. * pain visual analog scale (vas) ≥4. * at least one active trigger point in the following muscles: pectoralis major, superior trapezius, serratus anterior, levator scapularis, latissimus dorsi, infraspinatus exclusion criteria: * current radiation therapy or time since completion \< 3months. * allergy to lidocaine or other local anesthetics * active infection over injection sites * unavailability to be at the hospital during study intervention.